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Density functional theory calculations and electronic structure analyses reveal a radical mechanism with spin-crossovers for C–H bond cross-coupling and N2 activation catalysed by β-diketiminate iron complexes.

A density functional theory study of copper-mediated dehydroacylation of 4-phenyl-2-butanone to the corresponding olefin reveals a flexible N–H transfer process and a metal-independent C–C cleavage mechanism.

Ortho-Fluorinated iron catalysts showed high activity in ethylene polymerization delivering two types of PEs with different end-groups. DFT studies on polymerization mechanism have explain the above-mentioned observations.

In this article, the side-entry agitator commonly used in the wet desulfurization absorption tower of a 300 MW thermal power unit was taken as the research object, and the gas–liquid two-phase flow field in the stirring tank was numerically simulated by using the two-fluid model based on Euler–Euler method. The vertical and horizontal velocity field distribution and gas phase distribution in the stirring tank were studied. The results showed that the side-entry agitator formed a “fountain” circulating flow in the stirring tank. The high-speed region of the liquid flow was mainly concentrated near the mixing blade and the bottom banded region. The range of large changes in the fluid velocity was mainly concentrated from the bottom of the mixing tank to 2–3 m from the bottom. The distribution of the oxidizing air was concentrated in the middle of the stirring tank. The mixing effect of two phases in the stirred tank was good, and the oxidizing air was fully diffused. The numerical study in this article has reference significance for in-depth understanding of the flow field and mixing effect of the side-entry agitator.

Although the methods of chemical reduction of graphene oxide have been intensively and well investigated, the reduction mechanism is still ambiguous to date. The reduction mechanisms proposed so far were limited to explain a specific reducing agent rather than a general accessible approach. Here, we suggest that the core issue of chemical reduction of graphene oxide is the reduction of hydroxyl groups. Fundamental reactions mechanisms - E1 and E1cB - are proposed and studied as a general applicable but conclusive reduction mechanisms. Density Functional Theory calculation was used to investigate both reaction pathways for the acid- and base-induced reductions. The calculation results show that both reaction pathways are favorable on kinetics and thermodynamics. By applying this reduction mechanism, we developed NaSH as a novel and efficient reducing agent to reduce GO at room temperature, which further confirms the feasibility of the proposed reaction pathways. This work is thus able to investigate possible reaction pathways for various chemical reduction methods and will help to mature novel reduction approaches.

A density functional theory study of Cu-catalyzed desaturation of δ-valerolactone into α,β-unsaturated counterparts reveals an unexpected binuclear di-tert-butyl peroxide (DTBP) homolysis with spin-crossover and a radical α-C-H bond activation mechanism. The rate-determining step in the reaction catalyzed by CuIOAc-CyPPh2 is the homolysis of the O-O bond in DTBP with a total free energy barrier of 26.9 kcal mol-1, which is consistent with the observed first-order dependences on LCuI-PR3 and DTBP, as well as the pseudo-zeroth-order with lactone. The α- and β-H transfer steps have 0.3 and 14.8 kcal mol-1 lower barriers than the O-O cleavage process, respectively. Such different barriers well explain the observed weak kinetic isotopic effect (KIE) at α-H and no KIE at β-H. In addition, we found that the replacement of CyPPh2 for pyridine in the Cu complexes leads to much higher barriers for O-O bond cleavage and C-H bond activations with the formation of more stable binuclear Cu complexes.

Density functional theory computations revealed a pivalic acid assisted C–H bond activation mechanism for rhodium catalyzed formation of α-branched amines with C–C and C–N bond couplings. The reaction energies of the [Cp*RhCl2]2 dimer and silver cations indicate that the Cp*RhCl+ cation is the active catalyst. The essential role of pivalic acid is a co-catalyst for the activation of the ortho-C(sp2)–H bond in phenyl(pyrrolidin-1-yl)methanone, while the reaction of NaHCO3 and HCl reduces the overall barrier of the catalytic cycle. In the presence of both pivalic acid and NaHCO3 in the reaction, the C(sp2)–H bond is activated through a concerted metallation deprotonation process, and the C–C bond coupling is the rate-determining step with a total free energy barrier of 23.9 kcal mol−1. Without pivalic acid and NaHCO3, the C(sp2)–H bond can only be activated through a σ-bond metathesis process and the free energy barrier increases to 32.2 kcal mol−1. We also investigated the mechanisms of a side reaction for β-branched amine formation and the reaction without styrene and found that their free energy barriers are 33.4 and 30.5 kcal mol−1, respectively.

In this work, fluorinated 2,6-bis(arylimino)pyridyl iron(II) complexes, [2-[CMeN{2,4-{(4-FC

2D anisotropic transport of photons/electrons is crucial for constructing ultracompact on-chip circuits. To date, the photons in organic 2D crystals usually exhibit the isotropic propagation, and the anisotropic behaviors have not yet been fully demonstrated. Now, an orientation-controlled photon-dipole interaction strategy was proposed to rationally realize the anisotropic and isotropic 2D photon transport in two co-crystal polymorph microplates. The monoclinic microplate adopts a nearly horizontal transition dipole moment (TDM) orientation in 2D plane, exhibiting anisotropic photon-dipole interactions and thus distinct re-absorption waveguide losses for different 2D directions. By contrast, the triclinic plate with a vertical TDM orientation, shows 2D isotropic photon-dipole interactions and thus the same re-absorption losses along different directions. Based on this anisotropy, a directional signal outcoupler was designed for the directional transmission of the real signals.

A density functional theory study of the aerobic oxidation of 1-phenylethanol into acetophenone catalysed by phenanthroline copper (phenCu) complexes reveals a binuclear O2 activation and hydrogen transfer mechanism with multiple spin-crossover steps. When di-tert-butyl azodicarboxylate (DBAD) exists, it acts as a stoichiometric oxidant and forms DBADH2 through successive transfers of the proton and hydride from 1-phenylethanol to DBAD in one transition state with a free energy barrier of 21.8 kcal mol−1. After the consumption of DBAD, DBADH2 acts as a co-catalyst assisting O2 activation and acetophenone formation through binuclear transition states for the cleavages of O–O and C–H bonds with a total free energy barrier of 24.6 kcal mol−1. Without the presence of DBAD or DBADH2, the total free energy barrier for the aerobic oxidation of 1-phenylethanol with the participation of two phenCu complexes is 26.1 kcal mol−1. In all the above three situations, the rate-determining step is the activation of the C–H bond in 1-phenylethanol. The formation of HOO˙ radical and the breaking of the O–O bond in hydrogen peroxide for the formation of a Cu(II)-hydroxyl dimer are also key steps in the reaction and need the participation of two phenCu complexes.

Inspired by the structure and optical properties of N,N′-dialkylated/dibenzylated 2,5-bis(4-pyridinium)thiazolo[5,4-d]thiazole, we proposed a series of disubstituted thiazolo[5,4-d]thiazole derivat...

Catalyst-free, additive-free and light-free aerobic conversion of benzylic C–H to CO bonds is reported. A series of C–H bonds in diphenylmethanes and benzyl ethers underwent this transformation to give the targeted products in low to high yields. The reaction mechanism was also investigated using radical trapping, DFT calculations and 18O-labelled experiments, and the results suggested that the present reaction relied on an activation of oxygen by the π bond of the benzene ring.

Bike-sharing system has been launched in many cities, due to the essential merits. Along with the convenience brought by the rapid development of bike-sharing system, several severe problems also arise. The most serious problem is the uneven distribution of bicycles. Thus the VRP model for bike-sharing inventory rebalancing and vehicle routing is formulated. Additionally, an improved particle swarm optimization (PSO) algorithm is designed to solve this problem. Finally, a case study is undertaken to test the validity of the model and the algorithm. Five maintenance trucks are designated to execute all delivery tasks required by 25 spots. Capacities of all of the maintenance trucks are almost fully utilized. It is of considerable significance for bike-sharing enterprises to make optimal bike schedule.

A detailed reaction mechanism of the hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline catalysed by a half-sandwich Cp*Ir triazolylidene complex was computationally investigated by using density functional theory. The direct proton transfer from Ir to the nitrogen atom in quinoline was found to be the rate-determining step with a total barrier of 25.1 kcal mol−1 in free energy. Furthermore, by replacing the hydrogen atoms at the para (R) positions of the pyridine ligand with different functional groups, and the triazolylidene ligands with various N-heterocyclic carbenes, we proposed a series of half-sandwich Ir, Rh, and Co complexes and computationally screened four promising candidates for the catalytic hydrogenation of quinoline to 1,2,3,4-tetrahydroquinoline with predicted total free energy barriers close to 24.0 kcal mol−1.

An aliphatic SNS manganese pincer complex is computationally predicted as a promising catalyst for the hydrogenation of acetophenone to 1-phenylethanol. Density functional theory (DFT) calculations indicate that the total free energy barrier is 26.6 kcal/mol. Detailed reaction dynamics processes of two key steps, methanol assisted H2 cleavage and hydrogenation of acetophenone, are analyzed by using ab initio molecular dynamics (AIMD) simulations. Our AIMD simulation results confirmed the proposed catalytic mechanism based on DFT calculations and revealed that the H2 cleavage happens between 0.3 and 0.7 ps, while the hydride transfer from Mn to carbon happens at around 0.1 ps.

Based on Internet technology, urban customized bus can meet the diverse and differentiated travel demands, and to a certain extent, can alleviate urban traffic congestion. Reasonable planning of customized bus routes can improve the travel efficiency of passengers and the operation efficiency of customized bus. This paper systematically reviews the domestic and foreign literature on customized bus route planning. Based on the analysis of the influencing factors on the layout of customized bus routes, this paper uses the interactive auxiliary system analysis method, combined with practical cases, and plans the customized bus routes from four aspects: demand analysis, station coverage analysis, initial optimal path determination and comparative analysis of planning schemes.

Urban transportation issues continue to emerge and evolve as a result of rapid urbanization, and the systematic and scientific assessment of urban mobility is becoming increasingly essential. In this work, a Pressure-State-Response (PSR) model with 25 indicators was established to reflect the status of urban mobility. Then, the importance of indicators was determined with the interval-valued intuitionistic fuzzy analytic hierarchy process (IVIF-AHP) method, and the fuzzy comprehensive evaluation (FCE) method was applied to assess the overall status of urban mobility. The validity of the proposed model was demonstrated using the mobility system of Beijing as a case study, and the pressure, state, and response scores were calculated. The proposed assessment model can help to improve urban transportation monitoring and can also provide a scientific foundation for future urban transportation policymaking, planning, and traffic management, thereby further ensuring the sustainable development of urban transportation systems.

Organic cocrystals with unique energy-level structures are potentially a new class of materials for the development of versatile solid-state lasers. However, till now, the stimulated emission in cocrystal materials remains a big challenge possibly because of the nonradiative charge-transfer (CT) transitions. Here, for the first time, we report organic cocrystal microlasers constructed by simultaneously tailoring the energy levels and cavity structures based on the intermolecular halogen-bonding interactions. The intermolecular interactions triggered different self-assembly processes, resulting in distinct types of high-quality resonant microcavities. More importantly, the halogen-bonding interactions alleviated intermolecular CT and thus brought about a favorable four-level energy structure for the population inversion and tunable lasing in the cocrystals.

Three unsymmetrical NNN ligands with a 2-hydroxypyridyl fragment were used to react with RuHCl(PPh3)3(CO), affording the three bidentate ruthenium hydride complexes [(R1-C5H3N-CH2-C5H3N-C5H3N-R2)Ru...

The disproportionation of formic acid to methanol catalyzed by a half-sandwich iridium complex, [Cp*Ir(bpy-Me)OH2]2+, was computationally investigated by using density functional theory. A newly proposed mechanism features three interrelated catalytic cycles, the dehydrogenation of formic acid to CO2 and H2, the hydrogenation of formic acid to formaldehyde with the formation of water, and the hydrogenation of formaldehyde to methanol. Methanol assisted proton transfer and direct C–O bond cleavage after hydroxyl deprotonation in two competitive pathways for the formation of formaldehyde are the rate-determining steps in the whole catalytic reaction. Calculation results indicate that the formation of formaldehyde from methanediol through direct cleavage of a C–O bond after hydroxyl deprotonation has a free energy barrier of 25.9 kcal/mol, which is 1.9 kcal/mol more favorable than methanol assisted proton transfer.

A density functional theory study on hydrogenation of carbon dioxide to formate and formamide catalysed by a Mn bipyridinol complex reveals an unexpected metal–ligand cooperation mechanism with concerted two-proton transfer processes for the activation of diethylamine and formic acid, as well as the formation of formamide and water. Both ortho-O atoms in the bipyridinol ligand act as proton relay sites for the simultaneous transfer of two protons for the breaking of N–H and C–O bonds and the formation of a C–N bond.

Invited for the cover of this issue is the group of Xinzhen Yang at Institute of Chemistry, Chinese Academy of Sciences. The image depicts a series of computationally designed iron, cobalt, and manganese cyclopentadienone catalysts for hydrogenation of carbon dioxide to methanol. Read the full text of the article at 10.1002/chem.201701200.

The mechanisms of the transfer hydroformylation reactions catalyzed by rhodium, cobalt, and iridium complexes were studied by using the density functional theory. There are nine stages in each catalytic cycle: oxidation addition and C−H activation, hydrogen transfer and benzoic acid dissociation, anti-insertion reaction (decarbonylation), β-H elimination, nucleophilic substitution 1 (S N 1) of ligand, C=C insertion, C=O insertion, coordination of benzoic acid and hydrogen transfer, and reductive elimination and aldehyde dissociation for catalyst regeneration. The total free energy barriers of the reactions catalyzed by Rh, Co and Ir complexes are 25.1 ( 3 Rh → TS 11,12-Rh ), 27.3 ( 1 Co → TS 5,6-Co ) and 41.5 ( 14 Ir → TS 14,1-Ir ) kcal/mol, respectively. Such barriers indicate that the newly proposed cobalt complex could be a potential low-cost catalyst for the transfer hydroformylation reaction under mild conditions. The electronic structures of key intermediates and transition states in the reactions were analyzed by using the natural bond orbital theory and the Multiwfn program.

A series of manganese and cobalt complexes with pendant amines, (PtBu2NtBu2)M(R1)(R2)(R3) (M = Mn, R1 = R2 = CO; M = Co, R1 = R2 = CN; R3 = H, CN, NO2, CH3, NH2, OH, CHO, COOH, COCH3, and COOCH3), were proposed and examined as potential catalysts for the production of methanol from CO2 and H2. Detailed mechanisms with three cascade catalytic reactions, the hydrogenation of CO2 to formic acid, the hydrogenation of formic acid to formaldehyde with the formation of water, and the hydrogenation of formaldehyde to methanol, are predicted and analyzed through density functional theory calculations. Among all proposed complexes, (PtBu2NtBu2)Co(CN)2(COOH) (1Co–COOH) and (PtBu2NtBu2)Co(CN)2(NH2) (1Co-NH2) are the two most active with total free energy barriers of 24.9 and 25.0 kcal mol−1, respectively. (PtBu2NtBu2)Mn(CO)2(COOH) (1Mn–COOH) and (PtBu2NtBu2)Mn(CO)2(NO2) (1Mn-NO2) are the most active manganese complexes with total free energy barriers of 26.6 and 27.7 kcal mol−1, respectively. Such low barriers indicate that these newly designed cobalt and manganese catalysts are promising low-cost catalysts for the conversion of CO2 and H2 to methanol under mild conditions.

Inspired by the structures of the active site of lactate racemase and recent reported SCS nickel pincer complexes, we built a series of scorpion-like SCS nickel pincer complexes with an imidazole tail and computationally predicted their catalytic activities for the racemization of lactic acid. Density functional theory calculations reveal a proton coupled hydride transfer mechanism for the dehydrogenation of l-lactate and the formation of d-lactate with a free energy barrier as low as 25.9 kcal mol-1.

A catalyst loading of between 0.001–0.05 mol% of the PNN-bearing ruthenium(II) complex [fac-PNN]RuH(PPh3)(CO) (PNN = 8-(2-diphenylphosphinoethyl)amidotrihydroquinoline), in combination with 5 mol% NaBH4, efficiently catalyzes the hydrogenation of esters to their corresponding alcohols under mild pressures of hydrogen. Both aromatic and aliphatic esters can be converted with high values of TON or TOF achievable. Mechanistic investigations using both DFT calculations and labeling experiments highlight the cooperative role of NaBH4 in the catalysis while the catalytically active species has been established as trans-dihydride [mer-PNHN]RuH2(CO) (PNHN = 8-(2-diphenylphosphinoethyl)aminotrihydroquinoline). The stereo-structure of the PNHN-ruthenium species greatly affects the activity of the catalyst, and indeed the cis-dihydride isomer [fac-PNHN]RuH2(CO) is unable to catalyze the hydrogenation of esters until ligand reorganization occurs to give the trans isomer.

Inspired by the structure and optical properties of

Inspired by the catalytic mechanism and active site structure of lactate racemase, three scorpion-like SCS nickel pincer complexes were proposed as potential catalysts for transfer hydrogenation of ketones and imines with ammonia-borane (AB) as the hydrogen source. Density functional theory calculations reveal a stepwise hydride and proton transfer mechanism for the dehydrocoupling of AB and hydrogenation of N-methylacetonimine, and a concerted proton-coupled hydride transfer process for hydrogenation of acetone, acetophenone, and 3-methyl-2-butanone. Among all proposed Ni complexes, the one with symmetric NH2 group on both arms of the SCS pincer ligand has the lowest free energy barrier of 15.0 kcal/mol for dehydrogenation of AB, as well as total free energy barriers of 17.8, 18.2, 18.0, and 18.6 kcal/mol for hydrogenation of acetone, N-methylacetonimine, acetophenone, and 3-methyl-2-butanone, respectively.

A density functional theory study of the asymmetric transfer hydrogenation of pyruvic acid to l- and D-lactic acids catalysed by a chiral osmium complex OsH[(R,R)TsNCH(Ph)CH(Ph)NH2](η6-p-cymene) reveals a formic acid assisted enantio-determining proton-coupled hydride transfer mechanism. Activation strain model analysis indicates that the C–H/π interaction between η6-arene and carboxyl ligands has a significant influence on the enantioselectivity. The replacement of p-cymene by 4-isopropyl biphenyl or phenyl is highly likely to improve the catalytic performance of the complex.

A series of amidate-ligated pentadentate iron and cobalt complexes with N-heterocyclic pyridinol groups were proposed and computationally screened as potential catalysts for CO2 reduction. Density functional theory calculations reveal a ligand assisted heterolytic H2 cleavage mechanism with a total free energy barrier of 23.3 kcal mol−1 for the hydrogenation of CO2 to methanol catalysed by a pentadentate Co complex with a 2-[bis(pyridine-2-ylmethyl)]amino-N-3,9-purin-2-one ligand.

Transit network optimization can effectively improve transit efficiency, improve traffic conditions, and reduce the pollution of the environment. In order to better meet the travel demands of passengers, the factors influencing passengers’ satisfaction with a customized bus are fully analyzed. Taking the minimum operating cost of the enterprise as the objective and considering the random travel time constraints of passengers, the customized bus routes are optimized. The K-means clustering analysis is used to classify the passengers’ needs based on the analysis of the passenger travel demand of the customized shuttle bus, and the time stochastic uncertainty under the operating environment of the customized shuttle bus line is fully considered. On the basis of meeting the passenger travel time requirements and minimizing the cost of service operation, an optimization model that maximizes the overall satisfaction of passengers and public transit enterprises is structured. The smaller the value of the objective function is, the lower the operating cost. When the value is negative, it means there is profit. The model is processed by the deterministic processing method of random constraints, and then the hybrid intelligent algorithm is used to solve the model. A stochastic simulation technique is used to train stochastic constraints to approximate uncertain functions. Then, the improved immune clonal algorithm is used to solve the vehicle routing problem. Finally, it is proved by a case that the method can reasonably and efficiently realize the optimization of the customized shuttle bus lines in the region.

The mechanism for the dehydrogenation of methanol-water mixture catalyzed by [K (dme) 2 ][RuH(trop 2 dad)] was studied by using the density functional theory method. We found that the imidazole ring acts as a “hydrogen reservoir” by taking the hydrogen atoms from methanol and water and releasing CO 2 and three hydrogen molecules. A direct hydride transfer route for the dehydrogenation of formic acid was revealed. Furthermore, we also investigated the solvent effect in the reaction and found that the solvent have significant influence on the structures and relative energies.

A combined experimental and computational investigation of the CO dissociation properties of three [Fe]-hydrogenase models, [(2-CH2CO-6-HOC5H3N)Fe(CO)3I] (1), [(2-CH2CO-6-MeOC5H3N)Fe(CO)3I] (2), and [(2-CH2CO-6-t-BuOC5H3N)Fe(CO)3I] (3), shows equilibria of tricarbonyl and dicarbonyl complexes in solution. In CH3CN, 1 transforms to the solvated product [(2-CH2CO-6-HOC5H3N)Fe(CO)2(CH3CN)I] (7). The reactivity of 2 with PPh3 was also explored, giving [(2-CH2CO-6-MeOC5H3N)Fe(CO)2(PPh3)I] (8) via one CO substitution by PPh3.

We found an ultraviolet (UV)-light induced formation of biphenyl and sodium benzoate from benzene and sodium carbonate. The reaction happens in the interface of benzene and aqueous solution at the room temperature. After 5 h of UV-light exposure, 11.4% of initial amount of 4.4 g (5.0 mL) benzene are converted to biphenyl and sodium benzoate, which are distributed in benzene and aqueous solution, respectively. Using density function theory (DFT) and time dependent DFT, we have investigated the mechanism of this light-induced reaction, and found that the sodium carbonate is not only a reactant for the formation of sodium benzoate, but also a catalyst for the formation of biphenyl.

Inspired by the active-site structure of the [NiFe] hydrogenase, we have computationally designed the iron complex [P(tBu) 2 N(tBu) 2 )Fe(CN)2 CO] by using an experimentally ready-made diphosphine ligand with pendant amines for the hydrogenation of CO2 to methanol. Density functional theory calculations indicate that the rate-determining step in the whole catalytic reaction is the direct hydride transfer from the Fe center to the carbon atom in the formic acid with a total free energy barrier of 28.4 kcal mol(-1) in aqueous solution. Such a barrier indicates that the designed iron complex is a promising low-cost catalyst for the formation of methanol from CO2 and H2 under mild conditions. The key role of the diphosphine ligand with pendent amine groups in the reaction is the assistance of the cleavage of H2 by forming a Fe-H(δ-) ⋅⋅⋅H(δ+) -N dihydrogen bond in a fashion of frustrated Lewis pairs.

A density functional theory (DFT) study reveals that dehydrogenation of ethanol catalyzed by aliphatic PNP pincer cobalt complexes, [(PNPEt)Co(H)(OMe)] (1a) and [(PNPEt)Co(H)(CH2SiMe3)] (1b) (PNPEt = bis(2-(diethylphosphino)ethyl)amine), undergoes a self-promoted mechanism, in which an ethanol assists the formation of H2 as a bridge for proton transfer. The calculated total free energy barriers of ethanol dehydrogenation catalyzed by 1a and 1b are 23.9 and 22.2 kcal mol−1, respectively, which indicate that 1b is a promising catalyst for the dehydrogenation of ethanol under mild conditions.

Inspired by the active site structure of [FeFe]-hydrogenase, we built a series of iron dicarbonyl diphosphine complexes with pendant amines and predicted their potentials to catalyze the hydrogenation of CO2 to methanol using density functional theory. Among the proposed iron complexes, [(P(tBu)2N(tBu)2H)FeH(CO)2(COOH)](+) (5COOH) is the most active one with a total free energy barrier of 23.7 kcal/mol. Such a low barrier indicates that 5COOH is a very promising low-cost catalyst for high-efficiency conversion of CO2 and H2 to methanol under mild conditions. For comparison, we also examined Bullock's Cp iron diphosphine complex with pendant amines, [(P(tBu)2N(tBu)2H)FeHCp(C5F4N)](+) (5Cp-C5F4N), as a catalyst for hydrogenation of CO2 to methanol and obtained a total free energy barrier of 27.6 kcal/mol, which indicates that 5Cp-C5F4N could also catalyze the conversion of CO2 and H2 to methanol but has a much lower efficiency than our newly designed iron complexes.

The ruthenium complex (8-(2-diphenylphosphinoethyl)aminotrihydroquinolinyl)(carbonyl)(hydrido)ruthenium chloride exhibited extremely high efficiency toward the coupling cyclization of γ-amino alcohols with secondary alcohols. The corresponding products, pyridine or quinoline derivatives, are obtained in good to high isolated yields. On comparison with literature catalysts whose noble-metal loading with respect to γ-amino alcohols reached 0.5–1.0 mol % for Ru and a record lowest of 0.04 mol % for Ir, the current catalyst achieves the same efficiency with a loading of 0.025 mol % for Ru. The mechanism of acceptorless dehydrogenative condensation (ADC) was proposed on the basis of DFT calculations; in addition, the reactive intermediates were determined by GC-MS, NMR, and single-crystal X-ray diffraction. The catalytic process is potentially suitable for industrial applications.

The hydrogenation of ethyl acetate to ethanol catalyzed by SNS pincer ruthenium complexes was computationally investigated by using DFT. Different from a previously proposed mechanism with fac-[(SNS)Ru(PPh3)(H)(2)] (5) as the catalyst, an unexpected direct hydride transfer mechanism with a mer-SNS ruthenium complex as the catalyst, and two cascade catalytic cycles for hydrogenations of ethyl acetate to aldehyde and aldehyde to ethanol, is proposed base on our calculations. The new mechanism features ethanol-assisted proton transfer for H-2 cleavage, direct hydride transfer from ruthenium to the carbonyl carbon, and C-OEt bond cleavage. Calculation results indicate that the rate-determining step in the whole catalytic reaction is the transfer of a hydride from ruthenium to the carbonyl carbon of ethyl acetate, with a total free energy barrier of only 26.9kcalmol(-1), which is consistent with experimental observations and significantly lower than the relative free energy of an intermediate in a previously postulated mechanism with 5 as the catalyst.

A series of cobalt and manganese cyclopentadienone complexes are proposed and examined computationally as promising catalysts for hydrogenation of CO2 to formic acid with total free energies as low as 20.0 kcal mol−1 in aqueous solution. Density functional theory study of the newly designed cobalt and manganese complexes and experimentally reported iron cyclopentadienone complexes reveals a stepwise hydride transfer mechanism with a water or a methanol molecule assisted proton transfer for the cleavage of H2 as the rate-determining step.

The urban multi-mode traffic system, which is composed of rail transit, bus and trolley bus, taxi (including online car Hailing), bicycle and walking, provides the basic guarantee for the daily travel of urban residents. Based on the analysis of urban multi-mode transportation system and network characteristics, the directed network diagram of multi-mode transportation system is constructed. Based on the research methods of related fields at home and abroad, aiming at the characteristics of urban residents’ travel, especially commuting travel, a multi-objective optimization model of urban residents’ travel scheme analysis from the perspective of travel time, travel cost, etc. is constructed. Considering the non-linear characteristics of the model, the multi-objective model is transformed into a single objective model, and the model is solved by CPLEX optimization software. Finally, the applicability and reliability of the model are verified by an example.

Visible-light-driven photoreduction of CO2 to energy-rich chemicals in the presence of H2 O without any sacrifice reagent is of significance, but challenging. Herein, Eosin Y-functionalized porous polymers (PEosinY-N, N=1-3), with high surface areas up to 610 m2 g-1 , are reported. They exhibit high activity for the photocatalytic reduction of CO2 to CO in the presence of gaseous H2 O, without any photosensitizer or sacrifice reagent, and under visible-light irradiation. Especially, PEosinY-1 derived from coupling of Eosin Y with 1,4-diethynylbenzene shows the best performance for the CO2 photoreduction, affording CO as the sole carbonaceous product with a production rate of 33 μmol g-1 h-1 and a selectivity of 92 %. This work provides new insight for designing and fabricating photocatalytically active polymers with high efficiency for solar-energy conversion.

Visible-light-driven photoreduction of CO

Density functional theory study of the hydrogenation of ethyl acetate catalysed by iridium complexes [Cp*Ir(bpy)OH2]2+ reveals a direct C-O bond cleavage mechanism with two cascade catalytic cycles for the hydrogenation of ethyl acetate to aldehyde and the hydrogenation of aldehyde to ethanol. Calculation results indicate that the rate-determining state in the whole catalytic reaction is the direct C-O bond cleavage for the formation of aldehyde and ethanol with a total free energy barrier of 25.5 kcal mol-1, which is 0.6 kcal mol-1 more favorable than the mechanism proposed by Goldberg and co-workers in their experimental study.

In popularization and application of new energy buses has become the pioneer for popularization and application of new energy vehicles in China. This article attempts to analyze the successional trend of new energy bus from the published promotion policies aspect. Firstly, this paper summarized the new energy bus promotion policies in China since 2009 and organized them into five parts, including popularizing demonstration plan, policy on financial subsidy, industry management policies, ST the purchase subsidy is more specialized and requires higher technical performance of vehicles; construction scale of charging infrastructure has been enlarged continuously and quality assurance standards are more pragmatic. Finally, policy suggestions for subsidy are presented.

Metal pincer complexes have exhibited excellent catalytic properties in fundamentally important hydrogenation and dehydrogenation reactions. However, the development of low-cost and high-efficiency base metal pincer complexes for such reactions is still a big challenge in organometallic chemistry and catalysis. Computational chemistry methods, especially the density functional theory, can contribute much more to our knowledge about the essence of chemical reactions and has become an indispensable tool for understanding mechanistic insights and predicting new structures and reactions. In this chapter, we would like to introduce some of our mechanistic studies of the hydrogenation of carbonyl compounds and dehydrogenation of alcohols catalyzed by metal pincer complexes, as well as our computational design of iron, cobalt, and manganese pincer complexes as potential catalysts for various hydrogenation and dehydrogenation reactions.

The mechanisms of hydrogenation and dehydrogenation reactions catalyzed by a series of aliphatic PNP cobalt pincer complexes, [(PNRPiPr)CoH]+ (R = H and CH2X; X = H, Me, NH2, OMe, OH, F, and Cl) and [(PNPiPr)CoH], are studied by density functional theory calculations. In the hydrogenation of propylene catalyzed by [(PNRPiPr)CoH]+, a propylene molecule first inserts into the Co–H bond to form a Co–C bond. Then a H2 molecule is inserted into the Co–C bond for the formation and release of propane. The influence of different substituents on the N atom of the pincer ligand for the hydrogenation process is investigated. The relations between the field/inductive effect (σF) and total free energy barriers and the properties of the lowest energy intermediates, including the Co–N bond lengths, the lowest unoccupied molecular orbital energies, and the Wiberg bond indices of Co–N bonds, are analyzed. The results show that σF plays a crucial role in the substituent effect. The mechanism of acceptorless dehydrogenation...